a trip on an expressway

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a trip on an expressway

by sanju09 » Thu Mar 24, 2011 4:16 am
During a trip on an expressway, Don travelled a total of x miles. His average speed on a certain 5 -mile section of the expressway was 30 miles per hour, and his average speed for the remainder of the trip was 60miles per hour. His travel time for the x-mile trip was what percent greater than it would have been if he had travelled at a constant rate of 60 miles per hour for the entire trip?
(A) 8.5
(B) 50
(C) x/12
(D) 60/x
(E) 500/x

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by HSPA » Thu Mar 24, 2011 5:07 am
Let x=65

For 5 miles he needs 10 minutes. for next 60 miles he needs 60min
case 2: 60m/h constant
he needs 65 min for 65 miles

How much 70 min is greater than to 65 min

5/65 *100 So I am going with E

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by selango » Thu Mar 24, 2011 5:12 am
Total Distance=X miles,Speed =60 miles/hr

Normal time taken=X/60

D1=5 miles S1=30 miles/hr,T1=1/6

D2=x-5 miles S2=60 miles/hr,T2=x-5/60

Total time taken=(1/6)+(x-5)/60

Percentage=([1/6)+(x-5)/60-(x/60)]/[(x/60)] * 100


Pick E